1. Field of the Invention
This invention relates to the production of a continuous product stream of lime slurry to a jobsite which is remote from a lime production plant.
2. Description of the Prior Art
Lime has a variety of uses. It is commonly used in treating waste water and sewage. It is used in agriculture to neutralize acidic soils and to provide nutrients for sustaining plant life. Lime is also used extensively in construction for the stabilization of soils and as a component in a variety of building materials.
Lime, as referred to in this description, can be quicklime (calcium oxide (CaO)), hydrated lime (calcium hydroxide (Ca(OH).sub.2) or lime kiln dust. Quicklime is usually in the form of lumps or pebbles. Dry hydrated lime is usually a powder. In order to further process lime and improve the ease with which it is handled, dry lime is often mixed with water to form a slurry. In the case of quicklime, the water reacts with the quicklime in an exothermic reaction to form hydrated lime. This is often referred to as slaking. During the slaking of quicklime, large amounts of heat are given off which can significantly raise the temperature of the slurry.
Lime slurries can be made in batches or in a continuous process. If a particular user requires a large amount of lime slurry at a particular site, large capacity slaking and storage tanks can be permanently located on the site. These tanks can usually provide a sufficient supply of lime and lime slurry for most operations. Oftentimes, however, it is not practical to provide permanent slaking or storage tanks for forming lime slurries. In the agricultural industry and in some construction industries, lime may be required only periodically or during certain seasons. Here the limited use of lime may not justify the investment required for constructing and maintaining large capacity processing tanks and equipment. In other industries the location of the job sites may change from day to day, such as in road construction, so that permanently located processing and storage tanks would be impractical. Here, lime slurries would have to be made at permanent lime processing facilities and then pumped into tanks to be hauled to the specific job locations.
Portable equipment for forming lime slurries which can be moved from site to site, such as that described in U.S. Pat. No. 4,329,090 and which is hereby incorporated by reference, has been developed. One of the advantages of this type of equipment is that hot lime slurries formed during the slaking of quicklime can be used almost immediately, before any significant temperature drop. The use of these hot lime slurries has many advantages. In cold weather, the high temperature lime slurries are less likely to freeze and react more readily in temperature dependent reactions. When water is to be driven off, the high temperature of the slurry reduces the amount of energy needed to evaporate the water.
One of the shortcomings of the portable processing equipment is that the lime slurries are made in individual batches. After the lime slurry has been depleted, another batch must be made on site. This can be several hours, delaying the supply of lime slurry. Often it is crucial to have a continuous, uninterrupted supply of lime slurry. In hot mix asphalt plants, for instance, the continuous feeding and control of lime is essential.
What is needed is a means for forming a lime slurry at a remote job site while allowing the slurry to be fed in an uninterrupted, continuous product stream at a known concentration.